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Objective: To study the effect of imaging parameters on the contrast of T1 weighted SPACE (Sampling Perfection with Application optimized Contrast using different angle Evolutions, a 3D TSE variant) at 3 T for high resolution imaging of intracranial plaques before contrast and with post-gadolinium induced enhancement, and evaluate its relevance to patients with intracranial atherosclerosis., Materials and Methods: Optimized parameters giving good T1 contrast between intracranial vessel wall and cerebrospinal fluid within a specific scan time and reasonable coverage were found by simulation and validated in a healthy volunteer study. Based on the results, a clinical protocol covering the three major intracranial arteries (middle cerebral arteries, basilar arteries, and petrous internal carotid arteries) was developed. It was applied in ten patients diagnosed with intracranial arterial lesions. The accuracy of the technique in depicting vessel lumen was assessed by comparison to contrast enhanced MR angiography. The contrast enhancement ratios of the vessel wall/plaque identified were analyzed., Results: Simulation and volunteer study showed that using T1 weighted SPACE, good T1 contrast between vessel wall and cerebrospinal fluid occurred at TR of around 1000 ms using an echo train length of 21 within 10 minutes at an isotropic spatial resolution of 0.5 mm. In the 10 patients, 24 plaques were identified in the various segments of the intracranial arterial system of which eight appeared normal on MR angiography. Post-contrast enhancement ratio of these plaques varied from 0% up to 156%., Conclusions: T1 weighted SPACE provides good T1 contrast between intracranial arterial wall and cerebrospinal fluid with high resolution and good coverage within a clinically acceptable scan time. It can depict plaques pre- and post-contrast along the vessels surrounded by cerebrospinal fluid in the intracranial arterial system, and would be a useful tool in the clinical assessment of intracranial arterial diseases., (Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: To develop and assess an efficient method to identify end-expiratory end-diastolic (ED) and end-systolic (ES) images for accurate quantification of left ventricular (LV) function in real-time cine imaging., Methods: ECG-free free-breathing real-time cine imaging was performed on short-axis slices of thirteen healthy volunteers at 3 Tesla. K-means cluster segmentation was applied to delineate the endocardial contour, from which the LV centroid and cavity area were determined in each cine image. LV centroid displacement along the superior-inferior direction was filtered to extract respiratory motion in each slice. End-expiratory ED and ES images were then identified and used for LV function quantification. Accuracy was evaluated with that measured from the slice-matched standard ECG-gated breathhold segmented cines using two-tail paired Student's t-tests, linear regression analyses and Bland-Altman plots. Intra- and interobserver variability was calculated for each imaging technique., Results: Qualitatively, end-expiratory ED and ES images identified with the proposed method agreed with those determined by frame-by-frame visual inspection in 97.5% of cases (P > 0.05). Quantitatively, good agreement of LV function indices between the real-time cine and the standard segmented cine was observed with averaged differences of 0.1 ± 0.9 g for myocardium mass, -0.3 ± 1.0 mL for ED volume, 0.2 ± 1.2 mL for ES volume, -0.2 ± 1.3 mL for stroke volume, and -0.3 ± 0.8% for ejection fraction. Paired LV function values exhibited strong correlation (r ≥ 0.96) and no significant difference (P > 0.05). The real-time cine and the standard segmented cine showed similar intra- (1.2-3.3% and 1.1-2.8%, respectively) and interobserver variability (2.6-6.9% and 1.8-4.8%, respectively) with all P-values > 0.05. All the variability was comparable with published results., Conclusion: Compared with the laborious frame-by-frame visual inspection, as conventionally adopted, the proposed method is efficient in analyzing real-time cines for the accurate quantification of LV function without excessively manual interactions., (© 2015 Wiley Periodicals, Inc.)

Quantitative T₂ mapping was recently shown to be superior to T₂-weighted imaging in detecting T₂ changes across myocardium. Pixel-wise T₂ mapping is sensitive to misregistration between the images used to generate the parameter map. In this study, utility of two motion-compensation strategies-(i) navigator gating with prospective slice correction and (ii) nonrigid registration-was investigated for myocardial T₂ mapping in short axis and horizontal long axis views. Navigator gating provides respiratory motion compensation, whereas registration corrects for residual cardiac and respiratory motion between images; thus, the two strategies provided complementary functions. When these were combined, respiratory-motion-induced T₂ variability, as measured by both standard deviation and interquartile range, was comparable to that in breath-hold T₂ maps. In normal subjects, this combined motion-compensation strategy increased the percentage of myocardium with T₂ measured to be within normal range from 60.1% to 92.2% in short axis and 62.3% to 92.7% in horizontal long axis. The new motion-compensated T₂ mapping technique, which combines navigator gating, prospective slice correction, and nonrigid registration to provide through-plane and in-plane motion correction, enables a method for fully automatic and robust free-breathing T₂ mapping., (Copyright © 2011 Wiley Periodicals, Inc.)

Accurate measurement of spatially variant noise in MR images acquired using parallel imaging techniques is challenging. Image-based noise measurement methods such as the subtraction method proposed by the National Electrical Manufacturers Association or the multiple acquisition method often cannot be applied in vivo due to motion and/or dynamic contrast changes. Based on the Karhunen-Loeve transform and random matrix theory, we propose a novel method to accurately assess the noise variance in image series bearing temporal redundancy. The method fits the probability density function of eigenvalues from the temporal covariance matrix of the image series to the Marcenko-Pastur distribution. The accuracy of our method was validated using numerical simulation and an MR noise measurement experiment. The ability of this method to derive the g-factor map of a static phantom was validated against the multiple acquisition method. The method was applied to in vivo cardiac and brain image series and the results agreed with subtraction and multiple acquisition methods, respectively. This new image-based noise measurement method provides a practical means of retrospectively evaluating the noise level and/or g-factor map from multiframe image series., ((c) 2010 Wiley-Liss, Inc.)

Purpose: To evaluate the feasibility of the dark blood fast spin echo (FSE) T1-weighted-Sampling Perfection with Application of optimized Contrasts using different flip angle Evolution (T1w-SPACE) sequence in assessing whole body arterial wall information from the extracranial carotids to the popliteal artery., Materials and Methods: Twenty-eight subjects were subjected to noncontrast, dark blood whole body magnetic resonance angiography (DB-WBMRA) using a T1w-SPACE sequence optimized for each of the individual stations: carotid artery, thoracic aorta, abdominal aorta, and thigh/superficial femoral artery (SFA). Image quality/vessel wall visualization and the time required to image the four stations were evaluated. Two observers checked the reproducibility of vessel wall depiction by performing quantitative measurements in registered initial and repeat studies (six subjects) of vessel wall and lumen area at 17 locations along the arterial tree., Results: In 25 of the 28 scanned subjects, dark blood arterial images acquired in approximately 1 hour total imaging time allowed whole body arterial vessel wall visualization. Quantitative measurements showed high correlation between the initial and repeat studies for each of the observers as well as high interobserver reproducibility (r > 0.95; P < 0.01)., Conclusion: DB-WBMRA using T1w-SPACE is feasible and can be performed with a high degree of reliability.

Real-time dynamic magnetic resonance imaging (MRI) typically sacrifices the signal-to-noise ratio (SNR) to achieve higher spatial and temporal resolution. Spatial and/or temporal filtering (e.g., low-pass filtering or averaging) of dynamic images improves the SNR at the expense of edge sharpness. We describe the application of a temporal filter for dynamic MR image series based on the Karhunen-Loeve transform (KLT) to remove random noise without blurring stationary or moving edges and requiring no training data. In this paper, we present several properties of this filter and their effects on filter performance, and propose an automatic way to find the filter cutoff based on the autocorrelation of the eigenimages. Numerical simulation and in vivo real-time cardiac cine MR image series spanning multiple cardiac cycles acquired using multi-channel sensitivity-encoded MRI, i.e., parallel imaging, are used to validate and demonstrate these properties. We found that in this application, the noise standard deviation was reduced to 42% of the original with no apparent image blurring by using the proposed filter cutoff. Greater noise reduction can be achieved by increasing the length of the image series. This advantage of KLT filtering provides flexibility in the form of another scan parameter to trade for SNR.

This study was performed by using an institutional review board-approved protocol, with waived informed consent and HIPAA compliance. The purpose of this study was to preliminarily evaluate a cine delayed-enhancement (DE) pulse sequence for depiction of wall motion and myocardial scar extent during a single acquisition. The technique is based on inversion-recovery single-shot balanced steady-state free precession magnetic resonance imaging. Cine DE images were acquired in 26 patients (18 men, eight women; age range, 25-84 years; mean age, 61 years+/-13 [standard deviation]). Image contrast was consistent throughout each series. Overall (ie, with both readers' scores averaged), the cine DE imaging-depicted wall motion was scored correctly in 71% of myocardial segments. Scar extent was scored correctly in 76% of segments; in no patient was scarring missed. Cine DE imaging is a promising technique for simultaneous visualization of wall motion and myocardial scar extent., (Copyright (c) RSNA, 2006.)

Purpose: To compare two multislice turbo spin-echo (TSE) carotid artery wall imaging techniques at 1.5 T and 3.0 T, and to investigate the feasibility of higher spatial resolution carotid artery wall imaging at 3.0 T., Materials and Methods: Multislice proton density-weighted (PDW), T2-weighted (T2W), and T1-weighted (T1W) inflow/outflow saturation band (IOSB) and rapid extended coverage double inversion-recovery (REX-DIR) TSE carotid artery wall imaging was performed on six healthy volunteers at 1.5 T and 3.0 T using time-, coverage-, and spatial resolution-matched (0.47 x 0.47 x 3 mm3) imaging protocols. To investigate whether improved signal-to-noise ratio (SNR) at 3.0 T could allow for improved spatial resolution, higher spatial resolution imaging (0.31 x 0.31 x 3 mm3) was performed at 3.0 T. Carotid artery wall SNR, carotid lumen SNR, and wall-lumen contrast-to-noise ratio (CNR) were measured., Results: Signal gain at 3.0 T relative to 1.5 T was observed for carotid artery wall SNR (223%) and wall-lumen CNR (255%) in all acquisitions (P < 0.025). IOSB and REX-DIR images were found to have different levels of SNR and CNR (P < 0.05) with IOSB values observed to be larger. Normalized to a common imaging time, the higher spatial resolution imaging at 3.0 T and the lower spatial resolution imaging at 1.5 T provided similar levels of wall-lumen CNR (P = NS)., Conclusion: Multislice carotid wall imaging at 3.0 T with IOSB and REX-DIR benefits from improved SNR and CNR relative to 1.5 T, and allows for higher spatial resolution carotid artery wall imaging., (Copyright 2006 Wiley-Liss, Inc.)

Purpose: To develop and test a delayed-enhancement imaging method for improving the contrast between myocardial infarction (MI) and blood pool., Materials and Methods: The T(2) of blood is significantly longer than that of acute or chronic MI. The proposed multi-contrast delayed-enhancement (MCODE) imaging method produces a series of images with both T(1) and T(2) weightings, which provides both excellent contrast between normal and infarcted myocardium, and between blood and MI., Results: The subendocardial border between MI and blood pool was easily discriminated in the T(2)-weighted image. The measured MI-to-blood contrast-to-noise ratio (CNR) was better in the T(2)-weighted image than in the T(1)-weighted image (22.5+/-8.7 vs. 2.9+/-3.1, mean+/-SD, N=11, P<0.001, for True FISP, and 19.4+/-10.8 vs. 3.9+/-2.3, N=11, P<0.001, for Turbo FLASH)., Conclusion: The MCODE method provides a significant improvement in the ability to easily discriminate subendocardial MI by providing a T(2)-weighted image with high contrast between blood and MI. MCODE should improve both the detection and accurate sizing of MI., (J. Magn. Reson. Imaging 2005. Published by Wiley-Liss, Inc.)

Seventeen patients underwent magnetic resonance (MR) imaging for myocardial viability with a protocol approved by the institutional review board and gave written informed consent. Breath-hold cine inversion-recovery segmented k-space true fast imaging with steady-state precession sequence, referred to as inversion time (TI) mapping, was performed to determine optimal TI for myocardial infarction inversion-recovery imaging. From TI mapping, optimal TI was 180-315 msec 10-15 minutes after administration of 0.15 mmol/kg of gadolinium-based contrast material. At that optimal TI, relative signal intensity of infarcted myocardium compared with uninfarcted myocardium was maximal (mean +/- standard deviation, 297.8% +/- 86.5), whereas signal-to-noise ratio of uninfarcted myocardium was minimal (4.5 +/- 1.2). When applied to conventional myocardial infarction inversion-recovery imaging, optimal TI resulted in nulling of signal intensity of uninfarcted myocardium in all patients and in excellent conspicuity of infarcted myocardium in all nine patients with visible infarction., ((c) RSNA, 2004)